Interpretive Summary: Potatoes used for French fry processing must meet stringent quality requirements in order to produce fries having the appearance and taste that customers expect. Sugar-end defect is a tuber quality disorder that causes unacceptable darkening of one end of French fries. This defect appears when environmental stress during tuber growth increases post-harvest activity of an enzyme that produces the sugars glucose and fructose at one end of the tuber. These two sugars form dark-colored products during frying. Acrylamide is another product formed from glucose and fructose and acrylamide consumption has raised health concerns worldwide because it may be a human carcinogen. Molecular tools were used to reduce the activity of the enzyme most responsible for glucose and fructose accumulation in tubers in order to determine if this approach could control sugar-end defect formation. The glucose and fructose content of tubers, the frequency of sugar-end defects, and the acrylamide amount in fried potato strips were strongly reduced in multiple potato lines. Thus this gene-silencing approach can minimize a long-standing tuber quality problem while providing consumers with attractive products that reduce health concerns related to dietary acrylamide.

Technical Abstract:
Sugar-end defect is a tuber quality disorder that causes unacceptable darkening of one end of French fries. This defect appears when environmental stress during tuber growth increases post-harvest vacuolar acid invertase activity at one end of the tuber. Reducing sugars produced by invertase form dark-colored Maillard reaction products during frying. Acrylamide is another Maillard reaction product formed from reducing sugars and acrylamide consumption has raised health concerns worldwide. Vacuolar invertase gene expression was suppressed using RNA interference to determine if this approach could control sugar-end defect formation. Invertase activity and reducing sugar content of tubers, and sugar-end defects and acrylamide amount in fried potato strips were strongly reduced in multiple transgenic potato lines. Thus invertase silencing can minimize a long-standing tuber quality problem while providing consumers with attractive products that reduce health concerns related to dietary acrylamide.